Luteinizing hormone releasing hormone (LRH) is a decapeptide presenting the following amino acid sequence:
P-Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH.sub.2. LRH is secreted by the hypothalamus and stimulates secretion of the pituitary hormone(s) known to regulate ovulation. Several modifications of LRH have been produced. Fujino et al., Biochem. Biophys. Res. Comm. 49, pp. 698-705 (1972). One modification of LRH recently produced is [D-Ala.sup.6 ]LRH. Monahan et al., Biochemistry, Vol. 12, No. 23, 4616 (1973).